He doesn't have a MAF - he has an AFM - completely different.
If you NEED an external wastegate, then your turbo is too big for the engine most times. (I know, I know - boost creep issues enter in here).
Before yougo that route, you're going to need better fueling, so I would start off with ECU and injectors on the stock, low stressed system, then add boost and bigger turbos after getting thinhs right first - and gaining better driveability...